You may have heard the term “leaky gut syndrome” discussed over the last few years as a scary intestinal disorder caused by grains, beans, milk, sugar, alcohol, other “foods of civilization,” and especially wheat.

Most of the talk about leaky gut comes from the Paleo diet community, but leaky gut is not a currently accepted medical diagnosis. While some of the claims about it have been overblown, as you’ll see, there is something to it, and your intestinal health can directly affect your recovery from exercise.  

The Truth About Intestinal Permeability and “Leaky Gut Syndrome”

For starters, actual celiac disease is rare, affecting only around 1% of people, and Crohn’s is even less common at 0.1-0.3%. As for wheat allergy, it has a prevalence of about 0.4% in children. So, less than 2% of people have a clear-cut, medically-diagnosable digestive issue related to gut permeability or bad reactions to wheat or gluten.

However, that isn’t the end of the story. Non-celiac gluten sensitivity is probably far more common, with prevalence rates ranging from 0.5% to 13%. Gluten sensitivity is often the main cause of irritable bowel syndrome (IBS), and many sufferers find their symptoms improve when they eliminate wheat.

However, gluten is not the only chemical that can damage the gut and increase intestinal permeability. Lectins — prevalent in beans, lentils, wheat, and seeds — react with the gut in a way that increase inflammation and intestinal permeability, likely contributing to autoimmune disease.

Wheat and many other foods such as beans contain FODMAPs, or short-chain carbohydrates that are hard for the human intestine to digest properly. There is currently a lot of debate over which is the bigger culprit — gluten or FODMAPs — but the important thing is that these foods are now known to cause gut issues for most people when eaten in sizable amounts.

Related: Should Athletes Follow a Low-FODMAP Meal Plan?

Alcohol also damages the gut and increases intestinal permeability, in addition to having other undesirable effects. Excessive caffeine intake can cause diarrhea, although it doesn’t seem to cause major, lasting damage to the gut.

How Does Gut Health Affect Your Workouts?

A damaged intestinal lining — a “leaky gut” — can obviously cause issues with nutrient digestion. This leads to nutrient deficiencies, with the most common being B vitamins, particularly B12 and folate, which are vital to the nervous system.

More broadly, a leaky gut causes chronic, systemic inflammation, which impairs exercise recovery in a variety of ways. 

First, chronic inflammation reduces muscles growth. This may be partly because systemic inflammation is linked to low testosterone levels, but that’s certainly not the only mechanism of action, and it’s not clear that inflammation is a direct cause of low testosterone.

Related: How Men and Women Unlock the Power of Hormones

Lasting inflammation is also linked to joint injuries, which — for most people — is a bigger deal than merely not gaining as much muscle or endurance. In fact, leaky gut and lectin intake in particular can lead to joint degradation.

So How Much Does Your Nutrition Need to Change?

For starters, you need to sharply limit your intake of the main culprits: wheat, barley, alcohol, and legumes including beans, lentils, and peanuts. That said, going full Paleo is not necessary (although it is a viable option).  

That said, there are ways to limit the damage. Traditional preparation methods such as selecting only sprouted or sourdough breads or thoroughly soaking beans can get rid of most of the offending chemicals. In fact, these methods are so effective than even people with full-blown celiac disease can often safely consume sprouted and sourdough breads.

Related: Eat This One Food to Avoid Mid-Workout Gut Rot

It also helps to occasionally test markers of systemic inflammation, like C-reactive protein and IL-6. If those are low, your nutrition is probably okay, but if they’re high, you may need to get stricter about cutting back on the offending foods.